Subterranean adaptation in termites: a low O2 and high CO2 condition enhances reproduction of queens
Eisuke Tasaki, Eisuke Tasaki , Yasuyuki Komagata , Yoshihito Iuchi , Kenji Matsuura
Laboratory of Insect Ecology, Kyoto University, Japan; Laboratory of Insect Ecology, Kyoto University, Japan ; Laboratory of Insect Ecology, Kyoto University, Japan ; Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Japan ; Laboratory of Insect Ecology, Kyoto University, Japan
Organisms living in harsh environments have physiological adaptations to their habitats and even take advantage of difficult conditions. Subterranean termites live in nest chambers formed in the wood and construct underground gallery networks, where tens of thousands of individuals are engaged in social labor. Therefore, we expect a hypoxic gas condition in the nests of subterranean termites especially in royal chambers deep inside the wood. Here we show that a low O2 and high CO2 condition enhances reproduction of termite queens. Using the method of downward displacement of water, we identified that the nest gas condition is characterized by a low O2 and high CO2 in the subterranean termite Reticulitermes speratus. Queens showed significantly greater fecundity in the low O2 condition as in royal chambers than in atmospheric gas conditions. Quantitative real-time PCR analysis revealed that the nest gas conditions significantly promoted the expression levels of the vitellogenin genes Vg1, Vg2, and Vg3 in the queens compared with atmospheric gas conditions. These results suggest that termite queens have physiological adaptations so as to perform high reproductive activities under the hypoxic condition in the royal chambers. This study provides important insights into the linkage between nest environment and physiological adaptations in the evolution of social insects.